The present invention relates to automatic soap dispensers which eject a measured amount of liquid soap upon the request of a user without requiring the user to touch any part of the dispenser. It is particularly directed to such a dispenser having a positive displacement plunger type pump and a dispensing nozzle having no moving parts.
Automatic soap dispensers are known. They have general application to public restrooms in hotels, theatres, airports, and the like. Usually operated by light, sound or proximity sensors, such devices include some form of vibratory pump which, upon energization, cycles for a preset period. Such devices also usually include some form of dispensing nozzle which usually includes a shut off valve. These valves are prone to clogging which renders the device unusable or causes costly leaks.
A desirable feature in a dispenser of the type described is that it be responsive to a demand for soap without delay occasioned by priming a void between the pump and the nozzle. This requires soap to be present at the nozzle and that the pump be effective to move the soap out of the nozzle immediately on demand. This condition of the dispenser cannot be allowed to result in soap dripping from the nozzle. Means must be provided to reliably contain the soap just inside the nozzle as it awaits the next operation of the dispenser.